< draft-ietf-dnsop-nsec-aggressiveuse-08.txt		draft-ietf-dnsop-nsec-aggressiveuse-09.txt >
	Network Working Group K. Fujiwara		Network Working Group K. Fujiwara
	Internet-Draft JPRS		Internet-Draft JPRS
	Updates: 4035 (if approved) A. Kato		Updates: 4035 (if approved) A. Kato
	Intended status: Standards Track Keio/WIDE		Intended status: Standards Track Keio/WIDE
	Expires: July 16, 2017 W. Kumari		Expires: October 1, 2017 W. Kumari
	Google		Google
	January 12, 2017		March 30, 2017
	Aggressive use of DNSSEC-validated Cache		Aggressive use of DNSSEC-validated Cache
	draft-ietf-dnsop-nsec-aggressiveuse-08		draft-ietf-dnsop-nsec-aggressiveuse-09
	Abstract		Abstract
	The DNS relies upon caching to scale; however, the cache lookup		The DNS relies upon caching to scale; however, the cache lookup
	generally requires an exact match. This document specifies the use		generally requires an exact match. This document specifies the use
	of NSEC/NSEC3 resource records to allow DNSSEC validating resolvers		of NSEC/NSEC3 resource records to allow DNSSEC validating resolvers
	to generate negative answers within a range, and positive answers		to generate negative answers within a range, and positive answers
	from wildcards. This increases performance / decreases latency,		from wildcards. This increases performance / decreases latency,
	decreases resource utilization on both authoritative and recursive		decreases resource utilization on both authoritative and recursive
	servers, and also increases privacy. It may also help increase		servers, and also increases privacy. It may also help increase
	skipping to change at page 2, line 7 ¶		skipping to change at page 2, line 7 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.		Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on July 16, 2017.		This Internet-Draft will expire on October 1, 2017.
	Copyright Notice		Copyright Notice
	Copyright (c) 2017 IETF Trust and the persons identified as the		Copyright (c) 2017 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	skipping to change at page 2, line 41 ¶		skipping to change at page 2, line 41 ¶
	5.1. NSEC . . . . . . . . . . . . . . . . . . . . . . . . . . 6		5.1. NSEC . . . . . . . . . . . . . . . . . . . . . . . . . . 6
	5.2. NSEC3 . . . . . . . . . . . . . . . . . . . . . . . . . . 6		5.2. NSEC3 . . . . . . . . . . . . . . . . . . . . . . . . . . 6
	5.3. Wildcards . . . . . . . . . . . . . . . . . . . . . . . . 6		5.3. Wildcards . . . . . . . . . . . . . . . . . . . . . . . . 6
	5.4. Consideration on TTL . . . . . . . . . . . . . . . . . . 7		5.4. Consideration on TTL . . . . . . . . . . . . . . . . . . 7
	6. Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . 7		6. Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . 7
	7. Update to RFC 4035 . . . . . . . . . . . . . . . . . . . . . 8		7. Update to RFC 4035 . . . . . . . . . . . . . . . . . . . . . 8
	8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8		8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
	9. Security Considerations . . . . . . . . . . . . . . . . . . . 8		9. Security Considerations . . . . . . . . . . . . . . . . . . . 8
	10. Implementation Status . . . . . . . . . . . . . . . . . . . . 9		10. Implementation Status . . . . . . . . . . . . . . . . . . . . 9
	11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9		11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
	11.1. Change History . . . . . . . . . . . . . . . . . . . . . 10		11.1. Change History . . . . . . . . . . . . . . . . . . . . . 9
	11.1.1. Version draft-fujiwara-dnsop-nsec-aggressiveuse-01 . 13		11.1.1. Version draft-fujiwara-dnsop-nsec-aggressiveuse-01 . 13
	11.1.2. Version draft-fujiwara-dnsop-nsec-aggressiveuse-02 . 13		11.1.2. Version draft-fujiwara-dnsop-nsec-aggressiveuse-02 . 13
	11.1.3. Version draft-fujiwara-dnsop-nsec-aggressiveuse-03 . 13		11.1.3. Version draft-fujiwara-dnsop-nsec-aggressiveuse-03 . 13
	11.2. new section . . . . . . . . . . . . . . . . . . . . . . 13
	12. References . . . . . . . . . . . . . . . . . . . . . . . . . 13		12. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
	12.1. Normative References . . . . . . . . . . . . . . . . . . 13		12.1. Normative References . . . . . . . . . . . . . . . . . . 13
	12.2. Informative References . . . . . . . . . . . . . . . . . 14		12.2. Informative References . . . . . . . . . . . . . . . . . 14
	Appendix A. Detailed implementation notes . . . . . . . . . . . 14		Appendix A. Detailed implementation notes . . . . . . . . . . . 15
	Appendix B. Procedure for determining ENT vs NXDOMAN with NSEC . 15		Appendix B. Procedure for determining ENT vs NXDOMAN with NSEC . 15
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
	1. Introduction		1. Introduction
	A DNS negative cache exists, and is used to cache the fact that an		A DNS negative cache exists, and is used to cache the fact that an
	RRset does not exist. This method of negative caching requires exact		RRset does not exist. This method of negative caching requires exact
	matching; this leads to unnecessary additional lookups, increases		matching; this leads to unnecessary additional lookups, increases
	latency, leads to extra resource utilization on both authoritative		latency, leads to extra resource utilization on both authoritative
	and recursive servers, and decreases privacy by leaking queries.		and recursive servers, and decreases privacy by leaking queries.
	This document updates RFC 4035 to allow recursive resolvers to use		This document updates RFC 4035 to allow resolvers to use NSEC/NSEC3
	NSEC/NSEC3 resource records to synthesize negative answers from the		resource records to synthesize negative answers from the information
	information they have in the cache. This allows validating resolvers		they have in the cache. This allows validating resolvers to respond
	to respond with a negative answer immediately if the name in question		with a negative answer immediately if the name in question falls into
	falls into a range expressed by a NSEC/NSEC3 resource record already		a range expressed by a NSEC/NSEC3 resource record already in the
	in the cache. It also allows the synthesis of positive answers in		cache. It also allows the synthesis of positive answers in the
	the presence of wildcard records.		presence of wildcard records.
	Aggressive Negative Caching was first proposed in Section 6 of DNSSEC		Aggressive Negative Caching was first proposed in Section 6 of DNSSEC
	Lookaside Validation (DLV) [RFC5074] in order to find covering NSEC		Lookaside Validation (DLV) [RFC5074] in order to find covering NSEC
	records efficiently.		records efficiently.
	[RFC8020], and [I-D.vixie-dnsext-resimprove] proposes first steps to		[RFC8020] and [I-D.vixie-dnsext-resimprove] propose steps to using
	using NXDOMAIN information for more effective caching. This takes		NXDOMAIN information for more effective caching. This document takes
	this technique further.		this technique further.
	2. Terminology		2. Terminology
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in RFC 2119 [RFC2119].		document are to be interpreted as described in RFC 2119 [RFC2119].
	Many of the specialized terms used in this document are defined in		Many of the specialized terms used in this document are defined in
	DNS Terminology [RFC7719].		DNS Terminology [RFC7719].
	skipping to change at page 4, line 31 ¶		skipping to change at page 4, line 31 ¶
	attackers to cause a DoS (see additional resources), and also has		attackers to cause a DoS (see additional resources), and also has
	privacy implications (e.g: typos leak out further than necessary).		privacy implications (e.g: typos leak out further than necessary).
	Another example: assume that the (DNSSEC signed) "example.org" zone		Another example: assume that the (DNSSEC signed) "example.org" zone
	contains:		contains:
	avocado.example.org IN A 192.0.2.1		avocado.example.org IN A 192.0.2.1
	*.example.org IN A 192.0.2.2		*.example.org IN A 192.0.2.2
	zucchini.example.org IN A 192.0.2.3		zucchini.example.org IN A 192.0.2.3
	If a query is received for leek.example.org, it contacts its resolver		If a query is received for leek.example.org, the system contacts its
	(which may be itself) to query the example.org servers and will get		resolver (which may be itself) to query the example.org servers and
	back an NSEC record stating that there are no records		will get back an NSEC record stating that there are no records
	(alphabetically) between avocado and zucchini (or an NSEC3 record		(alphabetically) between avocado and zucchini (or an NSEC3 record
	stating there is nothing between two hashed names), as well as an		stating there is nothing between two hashed names), as well as an
	answer for leek.example.org, with the label count of the signature		answer for leek.example.org, with the label count of the signature
	set to two (see [RFC7129], section 5.3 for more details).		set to two (see [RFC7129], section 5.3 for more details).
	If the validating resolver gets a query for banana.example.org it		If the validating resolver gets a query for banana.example.org it
	will once again go off and query the example.org servers for		will once again go off and query the example.org servers for
	banana.example.org (even though it already has proof that there is a		banana.example.org (even though it already has proof that there is a
	wildcard record) - just like above, this has privacy implications,		wildcard record) - just like above, this has privacy implications,
	wastes resources, can be used to contribute to a DoS, etc.		wastes resources, can be used to contribute to a DoS, etc.
	skipping to change at page 7, line 15 ¶		skipping to change at page 7, line 15 ¶
	that name using the cached deduced wildcard. If the corresponding		that name using the cached deduced wildcard. If the corresponding
	wildcard record is not in the cache, it MUST fall back to send the		wildcard record is not in the cache, it MUST fall back to send the
	query to the authoritative DNS servers.		query to the authoritative DNS servers.
	5.4. Consideration on TTL		5.4. Consideration on TTL
	The TTL value of negative information is especially important,		The TTL value of negative information is especially important,
	because newly added domain names cannot be used while the negative		because newly added domain names cannot be used while the negative
	information is effective.		information is effective.
	Section 5 of [RFC2308] states that the maximum number of negative		Section 5 of [RFC2308] suggests a maximum default negative cache TTL
	cache TTL value is 3 hours (10800). It is RECOMMENDED that		value of 3 hours (10800). It is RECOMMENDED that validating
	validating resolvers limit the maximum effective TTL value of		resolvers limit the maximum effective TTL value of negative responses
	negative responses (NSEC/NSEC3 RRs) to this same value.		(NSEC/NSEC3 RRs) to this same value.
	Section 5 of [RFC2308] also states that a negative cache entry TTL is		Section 5 of [RFC2308] also states that a negative cache entry TTL is
	taken from the minimum of the SOA.MINIMUM field and SOA's TTL. This		taken from the minimum of the SOA.MINIMUM field and SOA's TTL. This
	can be less than the TTL of an NSEC or NSEC3 record, since their TTL		can be less than the TTL of an NSEC or NSEC3 record, since their TTL
	is equal to the SOA.MINIMUM field (see [RFC4035]section 2.3 and		is equal to the SOA.MINIMUM field (see [RFC4035]section 2.3 and
	[RFC5155] section 3.)		[RFC5155] section 3.)
	A resolver that supports aggressive use of NSEC and NSEC3 SHOULD		A resolver that supports aggressive use of NSEC and NSEC3 SHOULD
	reduce the TTL of NSEC and NSEC3 records to match the SOA.MINIMUM		reduce the TTL of NSEC and NSEC3 records to match the SOA.MINIMUM
	field in the authority section of a negative response, if SOA.MINIMUM		field in the authority section of a negative response, if SOA.MINIMUM
	skipping to change at page 9, line 18 ¶		skipping to change at page 9, line 18 ¶
	security problem.		security problem.
	It is also suggested to limit the maximum TTL value of NSEC / NSEC3		It is also suggested to limit the maximum TTL value of NSEC / NSEC3
	resource records in the negative cache to, for example, 10800 seconds		resource records in the negative cache to, for example, 10800 seconds
	(3hrs), to mitigate this issue.		(3hrs), to mitigate this issue.
	Although the TTL of NSEC/NSEC3 records is typically fairly short		Although the TTL of NSEC/NSEC3 records is typically fairly short
	(minutes or hours), their RRSIG expiration time can be much further		(minutes or hours), their RRSIG expiration time can be much further
	in the future (weeks). An attacker who is able to successfully spoof		in the future (weeks). An attacker who is able to successfully spoof
	responses might poison a cache with old NSEC/NSEC3 records. If the		responses might poison a cache with old NSEC/NSEC3 records. If the
	resolver is NOT making aggressive use of NSEC/NSEC3, the attacker has		resolver is not making aggressive use of NSEC/NSEC3, the attacker has
	to repeat the attack for every query. If the resolver IS making		to repeat the attack for every query. If the resolver is making
	aggressive use of NSEC/NSEC3, one successful attack would be able to		aggressive use of NSEC/NSEC3, one successful attack would be able to
	suppress many queries for new names, up to the negative TTL.		suppress many queries for new names, up to the negative TTL.
	10. Implementation Status		10. Implementation Status
	[ Editor note: RFC Editor, please remove this entire section.		[ Editor note: RFC Editor, please remove this entire section.
	RFC6982 says: "Since this information is necessarily time dependent,		RFC6982 says: "Since this information is necessarily time dependent,
	it is inappropriate for inclusion in a published RFC." ]		it is inappropriate for inclusion in a published RFC." ]
	Unbound currently implements aggressive negative caching, as does		Unbound currently implements aggressive negative caching, as does
	skipping to change at page 9, line 45 ¶		skipping to change at page 9, line 45 ¶
	and the Unbound developers.		and the Unbound developers.
	Thanks to Mark Andrews for providing the helpful notes for		Thanks to Mark Andrews for providing the helpful notes for
	implementors provided in Appendix B.		implementors provided in Appendix B.
	The authors would like to specifically thank Stephane Bortzmeyer (for		The authors would like to specifically thank Stephane Bortzmeyer (for
	standing next to and helping edit), Ralph Dolmans, Tony Finch, Tatuya		standing next to and helping edit), Ralph Dolmans, Tony Finch, Tatuya
	JINMEI for extensive review and comments, and also Mark Andrews,		JINMEI for extensive review and comments, and also Mark Andrews,
	Casey Deccio, Alexander Dupuy, Olafur Gudmundsson, Bob Harold, Shumon		Casey Deccio, Alexander Dupuy, Olafur Gudmundsson, Bob Harold, Shumon
	Huque, John Levine, Pieter Lexis, Matthijs Mekking (who even sent		Huque, John Levine, Pieter Lexis, Matthijs Mekking (who even sent
	pull requests!) and Ondrej Sury. Mark Andrews also provided the		pull requests!) and Ondrej Sury.
	helpful notes for implementors (https://www.ietf.org/mail-
	archive/web/dnsop/current/msg18332.html) which we made into
	Appendix B.
	11.1. Change History		11.1. Change History
	RFC Editor: Please remove this section prior to publication.		RFC Editor: Please remove this section prior to publication.
			-08 to -09:
			o Made RFC5074 Informative (after discussions with chairs.
			o Addressed SecDir comments.
			o Addressed OpsDir comments.
			-06 to -08:
			o Largely editorial, but please see the diffs (editors forgot to
			update change log when editing, backfilling change log.)
			o Changed "replacement" text to be "DNSSEC enabled validating
			resolvers SHOULD use wildcards ..." to align with text in doc.
			o "A resolver that supports aggressive use of NSEC and NSEC3 SHOULD"
			(should -> SHOULD) - to align with rest of text.
	-05 to -06:		-05 to -06:
	o Moved some dangling text around - when the examples were added		o Moved some dangling text around - when the examples were added
	some text added in the wrong place.		some text added in the wrong place.
	o There were some bits which mentioned "negative" in the title.		o There were some bits which mentioned "negative" in the title.
	o We had the cut-and-paste of what changed in 4035 twice.		o We had the cut-and-paste of what changed in 4035 twice.
	o Clarified that this also allows NODATA responses to be		o Clarified that this also allows NODATA responses to be
	skipping to change at page 13, line 36 ¶		skipping to change at page 13, line 41 ¶
	o Added "Partial implementation"		o Added "Partial implementation"
	o Section 4,5,6 reorganized for better representation		o Section 4,5,6 reorganized for better representation
	o Added NODATA answer in Section 4		o Added NODATA answer in Section 4
	o Trivial updates		o Trivial updates
	o Updated pseudo code		o Updated pseudo code
	11.2. new section
	12. References		12. References
	12.1. Normative References		12.1. Normative References
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119,		Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
	DOI 10.17487/RFC2119, March 1997,		RFC2119, March 1997,
	<http://www.rfc-editor.org/info/rfc2119>.		<http://www.rfc-editor.org/info/rfc2119>.
	[RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS		[RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS
	NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998,		NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998,
	<http://www.rfc-editor.org/info/rfc2308>.		<http://www.rfc-editor.org/info/rfc2308>.
	[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.		[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
	Rose, "Protocol Modifications for the DNS Security		Rose, "Protocol Modifications for the DNS Security
	Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005,		Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005,
	<http://www.rfc-editor.org/info/rfc4035>.		<http://www.rfc-editor.org/info/rfc4035>.
	[RFC4592] Lewis, E., "The Role of Wildcards in the Domain Name		[RFC4592] Lewis, E., "The Role of Wildcards in the Domain Name
	System", RFC 4592, DOI 10.17487/RFC4592, July 2006,		System", RFC 4592, DOI 10.17487/RFC4592, July 2006,
	<http://www.rfc-editor.org/info/rfc4592>.		<http://www.rfc-editor.org/info/rfc4592>.
	[RFC5074] Weiler, S., "DNSSEC Lookaside Validation (DLV)", RFC 5074,
	DOI 10.17487/RFC5074, November 2007,
	<http://www.rfc-editor.org/info/rfc5074>.
	[RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS		[RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS
	Security (DNSSEC) Hashed Authenticated Denial of		Security (DNSSEC) Hashed Authenticated Denial of
	Existence", RFC 5155, DOI 10.17487/RFC5155, March 2008,		Existence", RFC 5155, DOI 10.17487/RFC5155, March 2008,
	<http://www.rfc-editor.org/info/rfc5155>.		<http://www.rfc-editor.org/info/rfc5155>.
	[RFC7129] Gieben, R. and W. Mekking, "Authenticated Denial of		[RFC7129] Gieben, R. and W. Mekking, "Authenticated Denial of
	Existence in the DNS", RFC 7129, DOI 10.17487/RFC7129,		Existence in the DNS", RFC 7129, DOI 10.17487/RFC7129,
	February 2014, <http://www.rfc-editor.org/info/rfc7129>.		February 2014, <http://www.rfc-editor.org/info/rfc7129>.
	[RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS		[RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
	skipping to change at page 14, line 39 ¶		skipping to change at page 14, line 39 ¶
	2015, <http://www.rfc-editor.org/info/rfc7719>.		2015, <http://www.rfc-editor.org/info/rfc7719>.
	12.2. Informative References		12.2. Informative References
	[I-D.vixie-dnsext-resimprove]		[I-D.vixie-dnsext-resimprove]
	Vixie, P., Joffe, R., and F. Neves, "Improvements to DNS		Vixie, P., Joffe, R., and F. Neves, "Improvements to DNS
	Resolvers for Resiliency, Robustness, and Responsiveness",		Resolvers for Resiliency, Robustness, and Responsiveness",
	draft-vixie-dnsext-resimprove-00 (work in progress), June		draft-vixie-dnsext-resimprove-00 (work in progress), June
	2010.		2010.
			[RFC5074] Weiler, S., "DNSSEC Lookaside Validation (DLV)", RFC 5074,
			DOI 10.17487/RFC5074, November 2007,
			<http://www.rfc-editor.org/info/rfc5074>.
	[RFC8020] Bortzmeyer, S. and S. Huque, "NXDOMAIN: There Really Is		[RFC8020] Bortzmeyer, S. and S. Huque, "NXDOMAIN: There Really Is
	Nothing Underneath", RFC 8020, DOI 10.17487/RFC8020,		Nothing Underneath", RFC 8020, DOI 10.17487/RFC8020,
	November 2016, <http://www.rfc-editor.org/info/rfc8020>.		November 2016, <http://www.rfc-editor.org/info/rfc8020>.
	[root-servers.org]		[root-servers.org]
	IANA, "Root Server Technical Operations Assn",		IANA, "Root Server Technical Operations Assn",
	<http://www.root-servers.org/>.		<http://www.root-servers.org/>.
	Appendix A. Detailed implementation notes		Appendix A. Detailed implementation notes
End of changes. 18 change blocks.
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